Method of controlling the connection of the multiplier on the pressure piston of a multiple pressure casting machine

ABSTRACT

In a die-casting machine having a pressure piston for applying pressure to metal during introduction thereof into the mould and having a multiplier for applying an increased thrust to the pressure piston during a final phase of each casting operation, actuation of the multiplier is effected in dependence upon the position of the pressure piston during its stroke, thus eliminating costly previously used timing and actuation mechanism.

United States Patent 1191 Bohnlein et a1.

[ Oct. 23, 1973 "Filedf METHOD OF CONTROLLING THE CONNECTION OF THE MULTIPLIER ON THE PRESSURE PISTON OF A MULTIPLE PRESSURE CASTING MACHINE lnventors: Friedrich Bohnlein; Georg Stollmann, both of Brescia, Italy idra Presser G. m.b.H., Stuttgart, Germany Assignee:

Nov. 22, 1971 Appl. No.: 201,075

US. Cl. 164/120, 164/314, 425/242 Int. Cl 322d 27/10, B291 1/06 Field of Search 164/113, 120, 155, 164/157, 314, 315; 42.5/D1G. 11, 159, 242, 247

I References Cited UNITED STATES PATENTS 2/1952 Beuschler 425/242 X 4/1953 Holder..... 3/1954 Lester 10/1970 Bachelier....

3,601,180 8/1971 Nef et al. 164/315 3,693,702 9/1972 Piekenbrink et al..... 164/314 3,330,003 7/1967 Eggenberger et a1 164/315 X FOREIGN PATENTS OR APPLICATIONS 829,941 1/1952 Germany 164/314 1,213,065 11/1970 Great Britain 164/157 1,233,060 5/1971 Great Britain 164/314 Primary Examiner-R. Spencer Annear Attorney-Kenwood Ross e t al.

{57] ABSTRACT In a die-casting machine having a pressure piston for applying pressure to metal during introduction thereof into the mould and having a multiplier for applying an increased thrust to the pressure piston during a final phase of each casting operation, actuation of the multiplier is effected in dependence upon the position of the pressure piston during its stroke, thus eliminating costly previously used timing and actuation mechanlsm.

4 Claims, 1 Drawing Figure METHOD OF CONTROLLING THE CONNECTION OF THE MULTIPLIER ON THE PRESSURE PISTON OF A MULTIPLE PRESSURE CASTING MACHINE This invention relates to die casting machines.

For the production of die-castings which are free from pores and shrink holes and which have a closegrained structure it has proved beneficial to introduce metal into the usual mould of a die-casting machine in several steps. In this way die-castings free from pores and having great strength and a fine surface finish can be obtained provided the walls of the mould are treated carefully. In this mode of operation of a die-casting machine, metal is forced into the mould, without interruption of movement, in three consecutive phases.

In the first phase the liquid metal is introduced at a comparatively low velocity and low pressure. In the second phase the velocity is increased very rapidly and the mould completely filled. After the filling of the mould there ensues a transition from the second phase to the third phase, in which flow of metal ceases, during this phase and the metal solidifies in the mould under a high pressure which brings about compression of the metal of the die-casting.

For the introduction of the metal into the mould in the several phases, and particularly for the application of high pressure in the third phase, die-casting machines can be equipped with a multiplier i.e. a device for increasing the pressure applied to the metal, during the third phase. Such die casting machines possess a ram, which is influenced by a pressure medium on one side thereof and on the other side acts on the metal. The multiplier can have a multiplier piston which is connectable to the press piston and, after the connection brings about a multiplication of the pressure exerted on the press piston, and thus the metal pressed thereby. This multiplier piston is arranged so as to be shiftable inside a cylinder of the multiplier communcating with the press piston cylinder.

To bring about the transition from the first phase, in which the press piston is advanced at a comparatively slow speed, to the second phase, in which an increase in the speed and in the pressure can be effected, a reversing valve is provided, which is, for example, actuated from the press piston, when this latter has reached the desired position during feeding of the metal into the mould. Through this reversing valve pressure lines loaded with differing pressures are connected in such a way that the press piston is exposed, in the first phase, to only comparatively slight pressure, but is exposed, in the second phase, to considerably increased pressure.

On a die-casting machine it is important that the multiplier piston does not carry out any movement during the feeding of the metal into the mould during the first and second phases, up to the filling of the mould, so that the multiplied pressure force is fully available for the application of the high pressure during the third phase. It is furthermore desirable to be able to adjust the time of operation of the multiplier during the filling of the mould. Also it is desirable that the magnitude of the multiplication be variable within wide limits.

Controls are known which are suitable for effecting a time delay inthe operation of the multiplier piston and make possible the adjustment of the length of the time delay and also can effect variation of the magnitude of the high pressure applied during the third phase within wide limits. However, these controls are expensive and complicated in construction and in operation.

An object of the present invention is to provide a diecasting machine wherein actuation of the multiplier is effected simply and automatically.

Accordingly the invention provides a method of controlling a die-casting machine having a multiplying piston, wherein actuation of said multiplier piston to cause it to influence the usual press piston of the machine is effected in dependence upon the position of said press piston chiefly at the end of feed of liquid metal into the mould.

The invention also provides a die-casting machine, for example a cold-chamber die casting machine, which comprises: a pressure reservoir connected to a multiplier biassing chamber of the machine and-in a connecting line of which a check valve is provided whose opening stroke can be adjusted and which valve has a closure member which can be subjected to the pressure in said pressure reservoir through a pressure medium; and a hydraulic reversing valve, controlled by a press piston, with a pilot valve in said line conducting the pressure medium for increase of said press piston velocity after. feeding liquid metal into the mould, said check valve for pressure actuation of the closure member in its closing direction being connected to said connecting line conducting pressure medium for said increase in said press piston velocity and being operable by means of said reversing valve for said closure member of said pilot valve.

The pressure force actuating the multiplier piston can be brought into action in dependence upon the position of the press piston at the end of the feed of liquid metal into the mould. Advantageously the actuating force of the multiplier piston is controlled by means of the switching element which initiates an increase in the speed of the press piston after the feed of the liquid metal.

When applying the method of the invention, actuation of the multiplier piston can be already initiated upon the transition from the first phase to the second 'phase. It has become apparent that, for many diecastings, the forcing of the metal into the mould can be effected in this manner, without defects in the structure or in the strength of the cast'parts occurring. Also the die casting machine is virtually not more highly stressed than known machines because the second phase as a rule only lasts for a short time, so that in the case of a certain interia of the multiplier connecting control media the multiplier piston is virtually also actuated only at the end of the second phase, as is the case with known machines which are substantially more expensive and require further additional controls.

The invention can be applied particularly to a coldchamber die-casting machine, which comprises a multiplier bias or pre-stressing chamber with a pressure reservoir connected thereto, and in the connecting line of which a check valve is incorporated and is adjustable in the opening stroke and has a closure member which can be opened to the pressure reservoir through pressure medium and which possesses a hydraulic reversing valve, controlled by the press piston, for a pilot valve in the connecting line conducting pressure medium for the rise in the pressure piston speed for the second phase after the feed of the liquid metal into the mould, if the check valve for the pressure impingement of its closure part in the blocking direction is connected to the connecting line conducting pressure medium for the increase in the press piston speed and is operable by means of the reversing valve for the pilot valve.

The usual reversing valve of the machine canbe used for the changing over of the pressure medium, acting in the first phase on the press piston, to the pressure medium, acting in the second phase, for the release of the blocking of the multiplier piston in very many cases additional structural elements being scarcely needed.

In case of need, the machine of the invention can also be modified, with slight expenditure, in such a way that the time interval from the actuating impulse for the connecting of the multiplier until the carrying out of this connecting can be adjusted in a variable manner, it being only necessary that an adjustable time member, which can be effective hydraulically or electrically or pneumatically, be placed into the pressure medium circuit for the actuation of the check valve.

With its great simplicity, the invention additionally affords the advantage that the multiplier can be connected, independently of the pressures acting on the press piston in the first and second phase, to the press piston or to the shot or firing piston connected to this matter and acting on the metal.

The invention will be described further, by way of example, with reference to the accompanying drawings wherein the single FIGURE illustrates an injection part of a preferred embodiment of a cold-chamber diecasting machine of horizontal construction and conforming to the invention.

The machine comprises a press piston 2 slidably mounted in a press cylinder 1. Piston rod 3 of piston 2 carries, at its left hand end (not shown) the usual shot piston (which is also not shown) which forces metal into the mould (not shown) when the press piston 2 is shifted, by virtue of pressure medium action, in the direction of the arrow A, in the press cylinder 1. Connecting to the press cylinder 1 is a multiplier cylinder 4, in which a multiplier piston 5 is incorporated so as to be slidingly movable. Connected via a line 6 to a compressor bias chamber 7 is a pressure reservoir 8. Incorporated between this latter and the compressor biassing chamber 7 is a check valve 9, the opening stroke of which can be adjusted via a spindle 10.

For the movement under pressure of a closure member 11 in the blocking direction of the check valve 9 this is connected via a line 12 and a line 13 as well as lines 14 and 15 to a chamber 16, into which a connecting line 17 from a pressure reservoir 18 leads. The chamber 16 can be opened or shut off in relation to the multiplier piston 5 by means of a pilot valve. The stroke of the closure piece 19 of this pilot valve can be adjusted by means of a handwheel 20.

The line 14 is connected to a reversing valve 21 which is designed as a 4/2-way valve and which is connected via the line 22 to a 2/2-way valve 23, from which the line 24 connects to the line 13. The valve 23 represents, in conjunction with the adjustable throttle 25 and the check valve 26, a hydraulically acting timing member 27. The valve 23 is brought out of shown blocking position into the position connecting the line 24 to the line 22 when the reversing valve 21 is brought out of its reproduced position into its other position. Then the pressure in the pump feed line 29, which connects to the line 14, is brought into action'via the line 28 at the valve 23. Consequently this is brought, with the respectively set delay, into the position connecting the lines 22 and 24 to one another. The actuating of the reversing valve 21 is effected for instance from the piston rod 3 in known per se manner via a rodwork or system of rods and an electrical limit switch, not shown.

In the position of the reversing valve 21 shown in the drawing, the chamber 16 is connected via the lines 15, 14, 30 and 31 to the chamber 32. Consequently the closure piece 19 is kept in its represented closure position. The chamber 16 is furthermore connected via the lines l4, l3 and 12 to the chamber 33, so that the closure part 11 is also kept in its shown blocking position. As soon as the reversing valve 21 is, however, put into its other position, the chambers 32 and 33 are connected to the line 35 leading to the tank 34, so that the pressure of the ambient atmosphere prevails in those chambers. This makes itself felt to the effect that both the closure part 11 and the closure piece 19 are opened by the hydraulic counterpressure. The opening time of the closure part 11 can of course, as already mentioned, be delayed through the timing member 27. In this case, as soon as the reversing valve 21 is put into its other position and thus the chamber 32 is connected suddenly to the line 35 leading to the tank 34, the closure part 11 remains connected to the chamber 19, via the lines l2, 13, 31, 14 and 15 as well as the fixed throttle 37, and therewith under pressure andin the blocking position until, through switching of the timing member 27, the chamber 33 isconnected via the line 12, 24, 22, 30 also to the line 35 leading to the tank 34 and the closure part 11 thus opens. The trivial quantity of oil, still nevertheless afterflowing via the throttle 37, remains ineffective, since it is also carried off via the substantially more greatly dimensioned lines 24, 22, 30 and 35 to the tank 34. Thus, in the design shown, upon the actuating of the reversing valve 21 with the switching-in of the second phase the connecting of the multiplier 4, 5 is simultaneously initiated, inwhich connection this connecting, if no timing member 27 is present, or the delay thereof is set to zero, is effected immediately withthe reversal of the valve 21 and in which connection the same reversing valve 21, which is needed anyway for the switching of the closure piece 19, is utilised for the actuating of the check valve 9.

The invention is not limited to the precise details of the foregoing embodiment and variations can be made thereto within the scope of the following claims.

We claim:

1. A method of controlling a die-casting machine having a press piston and a multiplying piston comprising activating the multiplying piston by the position of the piston rod of the press piston after a first phase of compression when the press piston has reached a predetermined position in the mold and primarily at the end of the feeding of liquid metal into the mold.

2. A method as claimed in claim 1, wherein the force applied to the multiplying piston is controlled by a switching means for a switching initiating an increase in velocity of the press piston after the feed of the liquid metal. i

3. A die-casting machine, such as a cold-chamber die casting machine with a multiplier biasing chamber comprising: a press piston, a multiplying piston, a pressure reservoir connected to the multiplier biassing chamber and to a check valve having an adjustable opening stroke. and a closure member which can be subjected to the pressure in the pressure reservoir through a pressure medium, and a hydraulic reversing valve, controlled by the press piston, for a pilot valve in the line conducting the pressure medium for increase of the press piston velocity after feeding liquid metal into the mold, the check valve for pressure actuation of the closure member in its closing direction being conclosure member of the pilot valve, the movement of the multiplying piston being brought about by the pressure behind the press piston.

4. A machine as claimed in claim 3, wherein an adnected to the connecting line conducting pressure me- 5 justable timing member is provided in the pressure medium circuit for the actuation of the check valve. 

1. A method of controlling a die-casting machine having a press piston and a multiplying piston comprising activating the multiplying piston by the position of the piston rod of the press piston after a first phase of compression when the press piston has reached a pre-determined position in the mold and primarily at the end of the feeding of liquid metal into the mold.
 2. A method as claimed in claim 1, wherein the force applied to the multiplying piston is controlled by a switching means for a switching initiating an increase in velocity of the press piston after the feed of the liquid metal.
 3. A die-casting machine, such as a cold-chamber die casting machine with a multiplier biasing chamber comprising: a press piston, a multiplying piston, a pressure reservoir connected to the multiplier biassing chamber and to a check valve having an adjustable opening stroke and a closure member which can be subjected to the pressure in the pressure reservoir through a pressure medium, and a hydraulic reversing valve, controlled by the press piston, for a pilot valve in the line conducting the pressure medium for increase of the press piston velocity after feeding liquid metal into the mold, the check valve for pressure actuation of the closure member in its closing direction being connected to the connecting line conducting pressure medium for the increase in the press piston velocity and being operable by means of the reversing valve for the closure member of the pilot valve, the movement of the multiplying piston being brought about by the pressure behind the press piston.
 4. A machine as claimed in claim 3, wherein an adjustable timing member is provided in the pressure medium circuit for the actuation of the check valve. 